The monitoring of ground chemical and hydraulic properties is advantageously employed in different applications, such as for example, monitoring pore-water and ground contamination, irrigation control systems of agriculture crops, and for the study of soils and plants. For this purpose special tools are needed to provide accurate information on the fluids contained in the ground, and for monitoring the chemical properties of the water and/or contaminants percolating therein. The monitoring of the vadose zone, which is the layer of land above the zone of saturation (i.e., above the water table), is of particular interest in such applications. The vadose zone connects sources of on land surface pollution with the groundwater in the saturation zone, such that real-time monitoring of the vadose zone may substantially assist in controlling groundwater quality.
Instruments such as tensiometers and suction cups are commonly used nowadays to measure the soil water potential, and to obtain samples of soil pore-water. These instruments are based on the generation of hydraulic continuity between the soil pore-water and water within a cell, through a porous medium (such as porous ceramic, porous metal or porous polymer). While, tensiometers and suction cups may be effectively used in soil science and agricultural practice, their use is relatively limited to very shallow soil depths. Typically, the porous tip, which is usually made of brittle ceramic material, is pushed into the ground, if the soil is soft enough, or installed in a small-diameter hole specially drilled for that purpose, and thus these devices can not be used to collect information from deeper ground layers in the vadose zone.
U.S. Pat. No. 6,956,381 discloses a method and system for measuring permittivity and electrical conductivity in deep soil levels using a flexible TDR (time domain reflectometry) probes attached to the outer side of a flexible sleeve disposed in a borehole. The flexible sleeve is sealed to prevent leakage of a filling material, such that improved contact of the TDR probes with the walls of the borehole is obtained after placing said sleeve in the borehole and filling it with said filling material.
The methods described above provide solutions for continuous monitoring of the ground water content in deep sections of the vadose zone. Though water content is one of the most important hydraulic parameter required for the study of hydrological process in the vadose zone it is most important to have a method that would enlarge the range of monitored parameters and add real time information on the ground water potential and pore water chemical properties. Therefore there is still a need for suitable means for sampling and monitoring chemical and hydraulic properties in deep soil levels.
It is therefore an object of the present invention to provide a method and apparatus for collecting real-time continuous information from deep vadose zone layers.
It is another object of the present invention to provide a method and apparatus for monitoring infiltration processes in deep soil levels, and for determining the hydraulic conditions and chemical properties of the percolating water.
It is a further object of the present invention to provide sampling probes configurations adapted for installation in deep soil levels.
It is yet another object of the present invention to provide a method and apparatus which allow real time monitoring of contaminant migration in the vadose zone while enabling to obtain pore water samples from various depths for chemical analysis and measure the ground water potential.
Other objects and advantages of the invention will become apparent as the description proceeds.